Plastic bag with rectangularly shaped end construction



R. E. WHITE April 16, 1968 PLASTIC BAG WITH RECTANGULARLY SHAPED END CONSTRUCTION Filed June 16, 1966 INVENTOR.

United States Patent 3,378,190 PLASTIC BAG WITH RECTANGULARLY SHAPED END CONSTRUCTION Reid Evan White, Maumee, Ohio, assignor to Owens- Illinois, Inc., a corporation of Ohio Filed June 16, 1966, Ser. No. 557,935 3 Claims. (Cl. 229--62.5)

ABSTRACT OF THE DISCLOSURE This invention relates to an improved plastic bag formed by folding and end sealing operations on a tube of thermoplastic material. More particularly, the invention provides a bag construction wherein the primary seals utilized for securing the side and end flaps formed on the end of the tubular body are accomplished by heat seals so disposed that no mandrel need be inserted within the tubular body.

This invention relates to a bag of thermoplastic material with a tubular body and a rectangularly shaped end closure of novel and advantageous construction. More particularly, the invention relates to a bag of the foregoing type which may be formed from a length of seamless thermoplastic tubing and in which the end closure may be provided with strength-imparting heat seals at desirable locations by means operable from locations exteriorly of the tubular body of the bag without the need for effecting time-consuming reciprocatory relative movement between a heat sealing bar or back-up mandrel and the entire depth of the tubular body. The invention further relate to a bag of thermoplastic material with a tubular body and a rectangularly shaped end closure which is provided, along one of the shorter sides thereof, with a filling valve which permits rapid filling of the completed ba-g through the valve with, for example, a granulated product such as fertilizer, and which closes under the weight of the product in the filled bag to prevent product leakage in shipment.

For a further understanding of the present invention, attention is directed to the following portion of the specification, the drawing, and the appended claims.

In the drawing:

FIG. 1 is a perspective view of a length of thermoplastic tubing from which a bag in accordance with the present invention may be formed;

FIGS. 2 and 3 are perspective views showing successive steps in the formation of a bag in accordance with the present invention from the length of tubing shown in FIG. 1;

FIG. 4 is a cross sectional view taken on line 44 of FIG. 3;

FIG. 5 is a perspective view of a tubular filling valve which may be incorporated in a bag in accordance with the present invention;

FIGS. 6 and 7 are perspective views showing additional successive steps in the formation of a bag in accordance with the present invention incorporating the filling valve of FIG. 5; and

FIG. 8 is a view, similar to FIG. 4, showing a step in the formation of a bag in accordance with an alternative embodiment of the present invention.

A bag in accordance with the present invention may be produced from a length of. plastic tubing T which is shown in FIG. 1. Tubing T may be desirably provided by cutting a section of predetermined length from a roll of lay-flat plastic tubing produced by any of several prior art continuous tubing extrusion systems. In the manufacture of shipping sacks for fertilizer and the like, for which the present invention is well suited, tubing T may be made 3,378,190 Patented Apr. 16, 1968 from polyethylene in the popular 5 mil wall thickness (0.005 in.) or from many other known suitable thermoplastic (heat-sealable) materials of suitable thickness.

A rectangularly shaped end closure construction may be incorporated in an end of the bag formed from tubing T (and preferably in both ends thereof) by providing four spaced-apart slots 11, 12, 13 and 14 extending parallel to one another from such end of the tubing length partially toward the other end. Slots 11-14 form, with one another, four closure flaps 15, 16, 17 and 18 arranged in an endless array and integrally attached to the tubular body portion 19 of tubing T which is disposed inwardly of the termini of slots 11-14. Closure flaps 15-18 include end closure flaps 15 and 17 and side closure flaps 16 and 18 which are arranged alternately with the end closure flaps. The end closure flaps 15 and 17 are of a width substantially equal to one another and the side closure flaps 16 and 18 are of a width substantially equal to one another and greater than the width of the end closure flaps.

In the first step of manufacturing a bag from the length of tubing T shown in FIG. 1, as shown in FIG. 2, end closure flaps 15 and 17 are each inwardly folded to overlie portions of the inner surfaces of side closure flaps 16 and 18 and each end closure flap is bonded to the underlying portions of the side closure flaps by heat seals 21 extending along the side edges of the end closure flaps. Heat seals 21 may be provided at such locations by means located exteriorly of the body portion 19 of the bag, shown schematically in outline as sealing bars S1 and S2, which are readily mechanized for high-speed production. Additionally, the locations of such heat seals are well situated to absorb the shearing forces between the side closure flaps and end closure flaps which are imparted by a fluent product packaged within the finished bag. Thus, other portions of the closure fiaps which must be bonded to one another to provide a sift-proof end closure construction and which are accessible to heat sealing means only by effecting reciprocatory relative movement of a sealing bar or back-up mandrel through the entire length of tubular body portion 19 of the bag, may be suitably bonded to one another by a readily applicable adhesive, as hereinafter described, notwithstanding the inherently weaker strength in shear of commonly used adhesives relative to a heat seal.

Subsequently, relative movement is effected between the partially-completed bag shown in FIG. 2 and a heat seal support mandrel M, as shown in outline in FIG. 3, and the portions of side closure fiaps 16 and 18 are inwardly folded so that the inner surface of the terminal edge of one of the side closure flaps, shown as flap 16, lies in engagement with the outer surface of the terminal edge of the other side closure flap (shown as flap 18). In this position the terminal edges of the side closure flaps are bonded to one another by a heat seal 22 extending therealon-g which may be effected by sealing bar S3, shown schematically in outline in FIG. 4.

A bag according to an alternative embodiment of the present invention in which the inner surfaces of the terminal edges of the side closure flaps are bonded to one another may be formed by substituting the heat sealing step shown in FIG. 8 for that shown in FIGS. 3 and 4. This type of seal can be eifected by well-known continuous band-type heat sealing machines, indicated schematically by heat seal bars S4 and S5 shown in outline, such as the Doughboy machine, somewhat more readily than the seal shown in FIGS. 3 and 4. However, a bag manufactured in this way has a shallow rib running laterally of the end closure which is somewhat objectionable from the standpoint of appearance.

Before the finished bag is formed from the partly fin ished bag shown in FIGS. 3 and 4 (or from the partly finished bag shown in FIG. 8) an adhesive 23 of a type suitable for bonding layers of the thermoplastic bag material to one another is applied to the outer surface of the inwardly folded end closure flaps and 17 by any of various prior art means suitable for the adhesive employed. Adhesive 23 is applied in such a manner that it extends continuously along the respective end closure flap in a pattern parallel to the terminal edge thereof to prevent product in the finished and filled bag from sifting out in a path over the outer surface of an end closure flap.

Adesive 23 may be any of a number of known hot-melt type adhesives used in bonding plastic layers together or any of a number of known aqueous resin emulsion adhesive systems. Solvent rubber-base pressure sensitive adhesive systems, on the other hand, have a rather low peel strength which make them less suitable for such an application. The application of the selected adhesive may be accomplished in a known manner (not shown), as by rolling or brushing.

In some cases it is desired to provide one end closure flap, shown as flap 17 in FIG. 6, with a filling valve 24 bonded thereto and extending inwardly past the terminal edge of such closure flap. Valve 24 may be desirably comprised of a one-half mil (0.0005 in.) section V of a length of seamless thermoplastic tubing, which is shown in FIG. 5. In any event, the valve 24 may be bonded to the upper surface of flap 17 by heat-sealing (not shown) or by the adhesive 23 placed thereon and in such a case it is also important to bond valve 24 to the overlying portions of side closure flaps in a continuous pattern extending parallel to the open ends of the valve to prevent product from sifting out of the bag over the top surface of valve 24. Thus, adhesive 23 is also applied to the exposed inner surfaces of side closure flaps 16 and 18 in a continuous pattern parallel to the adhesive pattern on the underlying end closure fiap 16. Adhesive may also be desirably applied to the inner surfaces of side closure flaps 16 and 18 in a similar pattern overlying the adhesive pattern on unvalved end closure flap is, as shown in FIG. 6. Subsequently, the flattened rectangularly shaped end closure(s) of the bag is(are) put into compression until adhesive 23 has set to effectively bond the side closure flaps to the underlying un-valved end closure flaps and to effectively bond the filling valve, if any, to the adjacent end and side closure flaps. After the removal of such compressive forces, the rectangularly shaped end structure E of a bag B in accordance with the embodiment of the invention depicted in FIGS. 1-6, will have the appearance shown in FIG. 7.

It is believed the best mode known to me to carry out this invention has been described above in terms sufiiciently full, clear, concise and exact as to enable any person skilled in the art to make and use the same. It is to be understood, however, that it is within my contemplation that certain modifications of the above-described mode of practicing the invention can be made by a skilled artisan without departing from the scope of the invention and it is, therefore, desired to limit the invention only in accordance with the appended claims.

I claim:

1. In a bag formed from thermoplastic sheet material and having a tubular body portion, a pair of side closure flaps integrally connected to the tubular body portion, a pair of end closure flaps integrally connected to the tubular body portion respectively intermediate said side closure flaps, said end closure flaps being narrower than the side closure flaps, each of said end closure flaps being inwardly folded to overlie an outwardly folded portion of each of the side closure flaps, and a heat seal along each side edge of each of the end closure flaps bonding said edge to the underlying side closure flaps; the improvement comprising the end portions of the side closure flaps being inwardly foldable so that their terminal edges are contiguous, a heat seal bonding said contiguous terminal edges of the side closure fiaps to each other, and subsequently applied adhesive means bonding the internal surfaces of each of said end portions of the side closure flaps to the underlying top surface portions of said end closure flaps.

2. A bag according to claim 1 wherein the inner surface of the terminal edge of one of the side closure flaps is bonded to the outer surface of the terminal edge of the other side closure flap.

3. A bag according to claim 1 wherein the inner surfaces of the terminal edges of the side closure flaps are bonded to one another.

References Cited UNITED STATES PATENTS 3,220,635 11/1965 Kasting, et al 229-625 3,261,267 7/1966 Becker 22962.5

FOREIGN PATENTS 961,222 6/ 1964 Great Britain. 1,359,073 3/ 1964 France.

JOSEPH R. LECLAIR, Primary Examiner.

R. PESHOCK, Assistant Examiner. 

